The New York Times has an interesting article on how the inversion of the yield curve is not isolated to the United States.

...the cash that is flowing from around the globe to China, in exchange for manufactured goods, and to the Middle East and emerging economies like Russia, in exchange for oil, isn't simply being plowed into Treasury bonds. It's being recycled into long-term government bonds in Japan, Britain and Germany, and thus is helping to keep interest rates low in those countries, too.